Pop-up sprinklers are well known and usually comprise a sprinkler body buried in the ground at or slightly below ground level. A nozzle is slidably contained within the body for axial movement and is normally retracted within the body by a retraction spring. When water under pressure is applied to the body, e.g. through a fluid inlet in the body, the water acts against the nozzle and pushes the nozzle upwardly against the bias of the retraction spring until a nozzle orifice located on the nozzle is above the ground. The top of the nozzle usually includes a cover for closing the normally open upper end of the body when the nozzle is retracted. Such sprinklers may include a rotary drive means for rotating the nozzle about a substantially vertical axis to water a circle or a portion thereof. Typical pop-up sprinklers known in the prior art are the large turf green driven rotors. i.e. the 630, 650, 660, 670, 680 or 690 Series, a manufactured by The Toro Company, the assignee of the present invention.
Since these above-noted sprinklers are often used in areas where people often walk or play such as golf courses, athletic fields, etc., the sprinklers are typically installed slightly below grade to prevent people from tripping on them. In such sprinklers, the nozzle often comprises a relatively small or slender nozzle body which contains the nozzle orifice. The nozzle body is sufficiently smaller than the diameter of the sprinkler body so that a considerable gap exists therebetween as the nozzle rises. Thus, it is not unusual for dirt and debris from the area surrounding the sprinkler to fall into this gap when the nozzle is popped up. Moreover, grass or other growing vegetation around the sprinkler body will also try to intrude its way into this gap and thereby impede the upward and downward movement of the nozzle.
U.S. Pat. No. 4,429,832 to Sheets recognizes the problems caused by the above-noted gap and discloses one attempted solution. In this patent, a sprinkler is disclosed in which a relatively rigid annular guard is fixedly attached to the nozzle by a plurality of attachment arms. The guard is relatively short and does not extend above the middle of the nozzle to allow the nozzle orifice at the upper end of the nozzle to clear the guard, as is necessary to conduct a sprinkling operation. While the guard is generally received inside the upper end of the sprinkler body, the guard is nonetheless located a substantial distance below the upper end of the body in the reflected position of the nozzle. As the nozzle rises under the influence of water pressure, the guard is projected up out of the body. When the nozzle is fully risen, the guard is located up above the body to seal the gap and prevent debris from falling into the body.
While the guard shown in the Sheets patent addresses the problems created by the gap, it has a number of shortcomings. For one thing, it requires some type of attachment means, such as the radiating arms, to rigidly secure it to the nozzle. To that extent, the guard is more difficult to manufacture and assemble since it requires a number of additional manufacturing or assembly steps, e.g. securing the arms both to the nozzle and the guard.
More importantly, the rigid attachment of the Sheets guard to the nozzle requires that the guard be below the nozzle orifice, and thus necessarily below the upper edge of the sprinkler body in the fully retracted position of the nozzle. With such a construction, the guard does not always effectively seal the gap. For example, during the initial upward rise of the nozzle, the guard does not reach the gap to begin sealing it until the nozzle has risen the amount which the guard is offset below the top of the body. Similarly, when the nozzle is being retracted, the guard passes back down into the sprinkler body before the nozzle is fully retracted, thereby allowing the gap to reappear during the final phases of the downward movement of the nozzle. Thus, the guard of the Sheets patent does not seal the gap over the full range of motion of the nozzle, thereby allowing some debris to fall into the sprinkler during the initial upward movement or final backward movement of the nozzle.